Silver alloy material and method for manufacturing the silver alloy material

ABSTRACT

The present invention provides a silver alloy material and a method for manufacturing the silver alloy material, the silver alloy material comprising essentially by weight of about 65% to 95% Ag, about 5% to 35% In. The silver alloy material has a solid-liquid coexistence zone. The steps for manufacturing the silver alloy material include mixing, heating in vacuum status, cooling and annealing. The characters of the silver alloy are low yield tensile strength (58 Mpa), high ultimate tensile strength (300 MPa) and high elongation (60%) and anti-tarnishing property. The silver alloy material could be used for optics reflector mirror, silver ornament, brazing materials and very fine silver alloy wire for semiconductor bounding application.

FIELD OF THE INVENTION

The present invention relates a silver alloy material, particularly, relates a silver alloy material with indium (In) and a method manufacturing thereof. The silver alloy material could be used for optics reflector mirror, silver ornament, brazing materials and very fine silver alloy wire for semiconductor bounding application.

BACKGROUND OF THE INVENTION

Pure gold material was used in wiring of chips in electrical products for a long time, but its high cost drives people of industry to look for replaceable material, such as copper wire. That copper wires are easy to be oxidized results in unstable operation of chips, and are overcome by adding electroplating gold, palladium (Pd) or Platinum (Pt). However, during wire bonding, a brazing interface is still subject to water vapor and further corroded. Consequently, on one hand, people of industry try to find alloy with different ratios of copper and gold for replacement of copper with gold, palladium or platinum. On the other hand, people of industry try to replace gold wire for wiring of pure silver, too.

Silver wires are advantageous because of better conductivity, lower cost, and less corrosion than copper wires. Though silver wires are more stable and not easy to be oxidized in atmosphere, however, they are subject to sulfuration. Alloy building has been developing in the field of silver utilization for overcoming sulfuration, such as improving the original characteristics of silver material by adding other elements, for example, palladium for improvement of anti-oxidation, anti-sulfuration and anti-electromigration.

Moreover, addition of various elements into alloy at same time is a trend in the field of alloy research. For example, U.S. Pat. No. 4,052,531 discloses a brazing alloy including by weight of 70% silver (Ag) and other percentages of indium (In), zinc (Zn), silicon (Si), and copper (Cu). Taiwan patent number TWI316092 discloses an alloy in which silver is as a basis, and indium (In), Tin (Sn), antimony (Sb), or bismuth (Bi). China patent publication number CN102312120A discloses an alloy bonding wire by weight of 96% to 97.5% silver and other percentages of indium (In) and gold (Au). Taiwan patent number TWI404809B discloses an alloy compound by weight of 64% to 67.5% silver and 31.5% to 35% indium, which has the characteristics of high hardness, high melting point, and high strength.

Accordingly, the applications of the alloy material is very broadly, however, mixing of two or more elements necessitates forming typical alloy material, and the typical alloy material is characterized by mixed specific elements with specific mixing ratios, which restricts application fields. Besides, the mixing of multiple elements might cause inhomogeneous alloy.

How to simplify the formation of an alloy material and forming an alloy material applied broadly are issues to be resolved.

SUMMARY OF THE INVENTION

Accordingly, a silver alloy material is provided and characterized by weight of 65% to 95% silver and 5% to 35% indium to form a solid-liquid coexistence zone.

Preferably, the silver alloy material includes by weight of 5% to 25% indium.

Preferably, the silver alloy material is applied for optics reflector mirrors.

Preferably, the silver alloy material is applied to brazing material.

Preferably, the silver alloy material is applied to silver ornaments.

Preferably, the silver alloy material is made as a wire in diameter of 8 mm to 16 um.

Preferably, the metal elongation of the silver alloy material is 60%.

Preferably, the yield tensile strength of the silver alloy material is 58 MPa.

Preferably, the ultimate tensile strength of the silver alloy material is 300 MPa.

A method for manufacturing a silver alloy material includes the steps: (a) providing silver particles and indium particles; (b) mixing the silver particles and the indium particles to form a silver-indium mixture; (c) vacuum heating the silver-indium mixture to enable the silver-indium mixture be homogenous in melting phase; (d) cooling the silver-indium mixture to form a primary silver-indium alloy, wherein the primary silver-indium alloy is a solid solution of silver-indium solid-liquid coexistence; and (e) annealing the primary silver-indium alloy to form the silver alloy material, wherein the silver alloy material has a solid-liquid coexistence zone.

Preferably, in the step (a), the total weight of the silver particles and the indium particles is a basis by weight of 65% to 95% silver and 5% to 35% indium.

Preferably, in the step (a), the weight percentage of the indium particle is further 5% to 25%.

Preferably, in the step (c), the silver particles and the indium particles are put into a pot and heated in temperature of 1000° C. to 1030° C.

Preferably, in the step (d), the silver-indium mixture is put into a vacuum apparatus for cooling.

Preferably, in the step (e), the primary silver-indium alloy is put into a vacuum apparatus for annealing.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:

The sole FIGURE is a schematic diagram illustrating a flow chart of providing alloy silver material according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A silver (Ag) alloy material with indium (In) and a method for manufacturing thereof are provided herein. Please refer to the FIGURE, the steps of forming the silver alloy material with Indium are illustrated as follows. Step S11: silver particles and indium particles are mixed to form a silver and indium (Ag—In) mixture. In step S11, the total weight of the Ag—In mixture is as a basis which includes by weight of 65% to 95% Ag and 5% to 35% In. In another embodiment, the Ag—In mixture may include by weight of 75% to 95% Ag and 5% to 25% In.

Next, step S12: vacuum heating is implemented. The Ag—In mixture is put into a vacuum furnace and heated at temperature of 1000° C. to 1030° C. to enable the Ag—In mixture be homogenous in molten phase.

Step S13 cooling is implemented. The heated Ag—In mixture is put into a vacuum apparatus for cooling to become a primary silver-indium alloy. Such the primary silver-indium alloy is a solid solution of Ag—In solid-liquid coexistence.

Step S14: annealing step is implemented after the cooling step. The primary silver-indium alloy is put into same or another vacuum apparatus for annealing to form a silver alloy material with indium. The softness, elongation, and toughness of the silver alloy material with indium may be enhanced by the annealing step. Moreover, the silver alloy material with indium has a solid-liquid coexistence zone.

An anti-sulfuration test is executed first. An optics reflector mirror made of the silver alloy material with indium and a plate made of pure silver (Ag) are put into a glass pot that contains sulfur (S) vapor and is at temperature of 120° C. and pressure of 1.01 Pa. After one hour, there is no sulfuration found on the optics reflector mirror made of the silver alloy material with indium. Oppositely, under same environment situation, the plate made of pure Ag is found to react with the sulfur vapor to form black argentic sulfide (Ag₂S) whose thickness is about 25 um after one hour. Compared with the sulfuration of the plate made of pure silver, the silver alloy material with indium, which includes by weight of 65% to 95% Ag and 5% to 35% In, has better anti-sulfuration characteristic.

Besides, pure Au, pure Ag, aluminum (Al), typical Ag alloy (by weight of 92.5% Ag and 7.5% Cu), and the silver alloy material with indium herein are measured according to ASTM standard.

The measured items include yields tensile strength, ultimate tensile strength, and elongation. A measurement sheet is as follows:

yields tensile ultimate tensile strength strength elongation Material measured (unit: MPa) (unit: MPa) (%) Silver material with Indium  58 300 60% Pure gold ~ 100 >20%   Pure silver ~ 170 ~ aluminum 15-20 40-50 ~ Typical silver alloy 124 283 41% (Ag = 92.5%, Cu = 7.5%)

As the measurement sheet, compared to Al or the typical Ag alloy, the yields tensile strength of the silver alloy material with indium is only 58 MPa. Provided that wires used in brazing of semiconductor chip package are made of the silver alloy material with indium, the lower yields tensile strength of the silver alloy material with indium, may reduce the loading of wire bonding tool and prevent the bonding pads of a chip from damages.

As the measurement sheet, compared to Al or the typical Ag alloy, the ultimate tensile strength of the silver alloy material with indium of the present invention is 300 Mpa that presents higher resistance and better loading against external force. Accordingly, the wires used in brazing of semiconductor chip package are made of the silver alloy material with indium of the present invention are capable of loading the impacts derived from subsequent injection. Furthermore, compared to the material disclosed in China patent publication number CN102312120A, the silver alloy material with indium of the present invention has the better ultimate tensile strength of 300 MPa (=300 MN/mm²) than Ag—In alloy bonding wire has the one of 70 MN/mm².

As the measurement sheet, the elongation of the silver alloy material with indium of the present invention is up to 60%, and such a characteristic may prevent wiring structures from being broken by external force during wire bonding or injection molding. Compared to China patent publication number CN102312120A, the silver alloy material with indium of the present invention has the better elongation than Ag—In alloy bonding wire has the one of 12%.

The wires made of pure Au or pure Ag just have a single melting point, such as Ag has the melting point of 961.93° C. and Au has the melting point of 1064° C. Consequently, during the wire brazing of the wires made of pure Au or pure Ag, it is necessary for wire bonding tools to be kept a single stable brazing temperature for sure the wires are steadily connected to a chip and a substance. It is advantageous for the silver alloy material with indium of the present invention to have a solid-liquid coexistence zone. When the wires made of the silver alloy material with indium of the present invention are brazed, the wire bonding tools may be kept at the temperature range that the solid-liquid coexistence zone exists. Consequently, both the rate of chip package and the yield of wire bonding are improved.

Accordingly, the silver alloy material of the present invention formed with silver and indium has anti-sulfuration, low yields tensile strength, high ultimate tensile strength, and high elongation, which could be used for optics reflector mirror, silver ornament, brazing materials. Besides, the characteristic of solid-liquid coexistence zone for the silver alloy material improves the yield of wire brazing. Consequently, the silver alloy material of the present invention is advantageous for the industry.

While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures. 

What is claimed is:
 1. A silver alloy material, a total weight of the silver alloy material as a basis, which is characterized in: by weight of 65% to 95% silver and 5% to 35% indium, wherein the silver alloy material has a solid-liquid coexistence zone.
 2. The silver alloy material of claim 1, wherein indium is included by weight of 5% to 25%.
 3. The silver alloy material of claim 1, wherein the silver alloy material is applied to optics reflector mirror.
 4. The silver alloy material of claim 1, wherein the silver alloy material is applied to brazing material.
 5. The silver alloy material of claim 1, wherein the silver alloy material is applied to silver ornaments.
 6. The silver alloy material of claim 1, wherein the silver alloy material is made as a wire in diameter of 8 mm to 16 um.
 7. The silver alloy material of claim 1, wherein the metal elongation of the silver alloy material is 60%.
 8. The silver alloy material of claim 1, wherein the yield tensile strength of the silver alloy material is 58 MPa.
 9. The silver alloy material of claim 1, wherein the ultimate tensile strength of the silver alloy material is 300 MPa.
 10. A method for manufacturing a silver alloy material, comprising: (a) providing silver particles and indium particles; (b) mixing the silver particles and the indium particles to form a silver-indium mixture; (c) vacuum heating the silver-indium mixture to enable the silver-indium mixture be homogenous in melting phase; (d) cooling the silver-indium mixture to form a primary silver-indium alloy, wherein the primary silver-indium alloy is a solid solution of silver-indium solid-liquid coexistence; and (e) annealing the primary silver-indium alloy to form the silver alloy material, wherein the silver alloy material has a solid-liquid coexistence zone.
 11. The method for manufacturing a silver alloy material of claim 10, wherein in the step (a), the total weight of the silver particles and the indium particles is a basis by weight of 65% to 95% silver and 5% to 35% indium.
 12. The method for manufacturing a silver alloy material of claim 11, wherein in the step (a), the weight percentage of the indium particle is further 5% to 25%.
 13. The method for manufacturing a silver alloy material of claim 10, wherein in the step (c), the silver particles and the indium particles are put into a pot and heated in temperature of 1000° C. to 1030° C.
 14. The method for manufacturing a silver alloy material of claim 10, wherein in the step (d), the silver-indium mixture is put into a vacuum apparatus for cooling.
 15. The method for manufacturing a silver alloy material of claim 10, wherein in the step (e), the primary silver-indium alloy is put into a vacuum apparatus for annealing. 